Apparatuses of the generic type are known, for example, from DE 103 46 195 B4 and DE 100 19 029 B4. For its intended purpose, an apparatus of this type is fixed on an oil cooler, in order to cool the oil in the internal combustion engine of a motor vehicle. In order to adapt the cooling performance of the apparatus to the current oil temperature, the temperature of a coolant which flows into the oil cooler is adapted by way of a thermostat valve. To this end, the thermostat valve has a warm inlet and a cold inlet. The cold inlet can be connected, for example, directly to a coolant outlet of a coolant cooler and can guide a relatively cold coolant into the thermostat valve. The warm inlet can be connected, for example, to a coolant outlet of the internal combustion engine and can guide a relatively warm coolant into the thermostat valve. The relatively cold coolant and the relatively warm coolant can be mixed with different proportions in the thermostat valve, in order to keep the oil in the oil cooler below a predefined temperature limit value and to make heating of the oil possible.
By way of the thermostat valve, the oil in the oil cooler is cooled as soon as the current oil temperature exceeds the predefined temperature limit value. As soon as the oil temperature undershoots the temperature limit value, said oil temperature is no longer regulated in the conventional apparatus. For this reason, the oil temperature and, as a consequence, also the viscosity of the oil in the oil cooler can differ considerably, which can lead to an increased fuel consumption and to a lower degree of efficiency of the internal combustion engine.
It is therefore the object of the invention to provide an apparatus of the generic type, in which the abovementioned disadvantages are avoided.